This invention relates generally to vehicle top boat carriers and more particularly to automatic boat loading and unloading carriers.
A number of mechanisms have been invented for loading and carrying a lightweight fishing boat or similar object on top of a vehicle. Many of the early designs incorporate simple racks to support and carry the boat but offer little assistance for loading and unloading. Some of them (U.S. Pat. Nos. 3,042,240; 3,044,643; 3,066,815; 3,064,841; 3,072,274; 3,139,203; 3,155,257; 3,311,246; and 3,363,788) allow the operator to place or hoist one end of the boat up on a support member and then lift the other end and swing it into place. This eliminates the need to lift the entire load straight up at once, allowing a solitary opreator to load heavier boats than would otherwise be possible.
Serveral of the early designs load the boat "semi-automatically" by means of mechanical lifting and turning mechanisms. They are more complicated, expensive to build and install than the foregoing racks, and lack flexibility. Some of these designs (U.S. Pat. Nos. 3,048,291 and 3,128,893) load a boat bow first in an upright position onto the top of a vehicle. Others of these devices (U.S. Pat. Nos. 2,967,635; 2,985,327; 3,435,970 and 3,478,908) load a boat from a position right side up on the ground and behind a vehicle to a position upside down on top of the vehicle in a more or less continuous motion. The latter, "up and over" technique requires considerable effort to raise and lower the boat and the effort required can vary dramatically during the course of loading and unloading. Also, once configured for a particular boat and vehicle combination, these systems are generally difficult to adapt and adjust for another boat or vehicle. Attempts to overcome these drawbacks have not succeeded.
U.S. Pat. No. 3,045,849 discloses an "up and over" system that uses pulleys, a pivoting arm which rises vertically from the center of the rack and articulated support arms to connect the stern of the boat to the rear of the vehicle not only to compound the leverage but also to change the direction of force applied to the loading lines.
A series of subsequent designs, shown in U.S. Pat. Nos. 3,696,953; 3,716,156; 3,777,922; 3,836,029; 3,905,499; 3,915,323; 3,930,584; 3,999,673 and 4,087,014, attempt to combine a winching arrangement with mechanical pivoting apparatus mounted at the rear of a vehicle to facilitate the "up and over" technique of loading. All of these are complicated, expensive designs and none are known to be in commercial production.
U.S. Pat. No. 3,387,727 shows the use of multiple pulleys on a continuous line arranged to provide different travel distances for a given amount of line travel. In this system, the boat must be manually inverted before loading and after unloading. This design, too, is complicated, cumbersome, expensive to build and difficult to install.
U.S. Pat. No. 3,435,970 illustrates the use of flexible lines attached to the top, rear of the vehicle to support the stern of the boat above the ground rather than using the complicated mechanical support means employed by most of the early designs. A vertical pole supports a pulley above the center rear of the vehicle to help direct and thereby reduce the tension needed on a single pull line connected to the bow of the boat.
U.S. Pat. No. 3,612,314 somewhat simplifies the earlier designs but lacks the ability to automatically tie the stern of the boat down and requires the operator to manually stow the stern lines.
U.S. Pat. No. 3,954,199 provides for powering the rear support roller and adds a roller at the rear, about which the boat pivots. The additional pivot member offers some assistance in adjusting the unit for satisfactory operation in certain installations by providing an intermediate "break-over" stage in the arc described by the boat. This design ties the stern down inherently, but fails to tie the bow down and requires several steps to operate the unit, such as switching the crank mechanism between rollers at various stages of the process.
The Electrolift boat loader, commercially available since about 1974, incorporates some of the features of both U.S. Pat. Nos. 3,612,314 and 3,954,199. It employs two rollers and ties the bow of the boat down but not the stern, as in the Cooper design (3,612,314). The stern support lines must be separately stowed. It utilizes a single bow line arrangement similar to the Grove design (3,954,199) but adds a spreader bar spanning the gunwales rearward of the bow. The lack of a separate pivot member renders this design difficult to adjust for satisfactory operation with certain vehicle and boat combinations.
U.S. Pat. No. 4,024,971 addresses the problem of tying the boat down all the way around as well as loading and unloading the unit in one continuous motion, and has been in commercial production. However, the line arrangement is complicated and requires that the length of the three line segments on each side be precisely coordinated with the location of the forward roller, pivot member, and the forward attaching points on the boat for proper operation and tie down. The unit is difficult to reconfigure once the line segments have been cut and braided back at each end and the entire assembly adjusted for a particular vehicle and boat.
U.S. Pat. No. 4,175,905 discloses an "up and over" loader set up so that the rear transverse member serves as both a roller and a line winch. A pair of lines extend around a front roller and back to a Y-line which is connected at two points on each gunwale of the boat. This arrangement is relatively simple but lacks the capability to automatically tie down the stern.
All of the above line-type loaders/unloaders incorporate a fixed mechanical advantage/line takeup ratio. This requires a compromise between loading/unloading effort and speed of operation. Significantly greater effort is required when first lifting the bow of the boat off the ground than in subsequent stages of the loading process. As the bow of the boat is elevated, the required effort diminishes greatly. In some designs, such as U.S. Pat. No. 3,836,029, the required force can reverse so that measures must be taken to keep the boat from crashing down onto the carrier. None of these designs optimizes the speed of operation as the required effort decreases.
Accordingly, a need remains for a boat loader that is simple, inexpensive, easy and safe to install and use, and can readily be adapted to different vehicles and boats.